Ed, you're trying to have it two ways. First you're saying that It'll be bad stations south of York lose service, then when we point out connecting services will still run, you say they shouldn't/can't run north of York. These are both wrong.
Firstly, HS2 should (and will) be extended to Newcastle via a Parkway in the Teeside conurbation (probably somewhere near Yarm), leaving the classic line free.
Second, the number of ECML paths given over to HS services will not be significant enough to take away all paths north of York for ECML services.
Thirdly, having 'fasts' stop will give services to places like Newark, Retford & Stevenage they don't currently get. At least an hourly LKX-Edinburgh will remain, as will connections to Hull, Leeds, Lincoln and Newcastle.
It would probably make more sense to have an Ashford-style solution at Darlington, with what really ought to be called HS3 using much of the alignment of the Ripon and Leamside lines to access the area, perhaps running alongside the A1 for some sections. Darlington has good connections for the Teesside area, and is certainly better than yet another station in a ploughed field (and we know how successful those have been in France, not to mention East Midlands Parkway).
The biggest problems with capacity down there are the Tyne bridges and the double-track Newcastle-Berwick-Edinburgh section, assuming that HS3 ends somewhere around Tyne Yard (which is the most sensible place to end it). Other than a new bridge, I honsetly cannot see what can be done about Newcastle. The route through Berwick might call for yet another new section, perhaps following the Coldstream route, but more likely parallel to the coast with all the curves straightened out. Still, for as long as we have those problems, we are limited in terms of the number of paths. Assuming we still want roughly the same number as the current EC, XC, TPX and Northern services crossing the bridges, then really only 2 or 3tph each direction can use the new line, two of which will have to leave/join the route at Darlington to serve York - unless the route runs through York anyway, in which case, we will not need to worry.
A new bridge could double the Newcastle service, although leaving or joining the route ar Darlington to cover York, Northallerton and Durham will be necessary. However, that still leaves us 1 or 2 tph for Edinburgh. Assuming it's two, that might be one semi-fast from King's Cross, that would call at Peterborough, Doncaster, York and Darlington at least, possibly a few other places as well, before going on to Newcastle, Morpeth, Alnmouth, Berwick and Dunbar. The HS3 trains (some from the Continent) would run non-stop from Newcastle to Edinburgh, and hopefully some (not the Continental ones) would go on to Aberdeen or Inverness. To get more than that, HS3 has to go all the way to Edinburgh.
On the WCML, I would apply something similar to Glasgow. The HS2 train would stop at Preston, Lancaster and Carlisle, while the WCML train would cover places such as Warrington, Wigan, Carnforth, Oxenholme, Penrith, Lockerbie and anywhere else I've forgotten.